Influência da catálise ácida e básica na preparação da sílica funcionalizada pelo método sol-gel

Some aspects of the chemistry involved in the preparation and characterization of functionalized silicon oxide by sol-gel method are considered in this work. The synthesis was performed with different silicon alcoxide precursors and the influence of the acid and basic catalyst was investigated. Characterization was performed by infrared absorption spectroscopy, elemental analysis and 29Si NMR. Infrared data show Si-C and -CH2- vibrational modes at 1250 to 1280 and 2920 to 2940 cm-1, respectively. The elemental analysis confirmed the presence of organic groups in the inorganic silica network. 29Si NMR results show different hydrolisys depending on the acid or base catalysis.

Influência do meio reacional no comportamento fotoquímico do inseticida paration etílico

The photodegradation of parathion in natural and dezionised waters was studied under irradiation at two different wavelengths: 280 nm and 313 nm. The influence of humic acids was evaluated. The results demonstrated that the degradation occurred only due to photochemical processes. The chemical hydrolysis and biological processes can be neglected in this case. The addition of humic acids did not increase the photodegradation rate in either water samples (natural or dezionised). In alkaline solutions the photodegradation rate was higher in dezionised water when compared to natural waters. The kinetic degradation in all experiments obeyed a first order reaction pattern.

Propelente sólido compósito polibutadiênico: I- influência do agente de ligação

In the Brazilian Complete Spacial Mission, the research of Vehicle Satellite Launcher is important. The solid propellant composite used in this vehicle is made with ammonium perchlorate, aluminiun powder and hydroxy terminated polibutadiene resin. In the propellant the bonding agent has a function to promote the interaction between solids and polimeric matrix, improving mechanical properties as stress, strain, aging characteristics and moisture embrittlement. Due its importance in propellant, bonding agent is consider as industrial secret and the literature about it is generic, without greater informations.

Influência da geometria da plataforma na determinação de chumbo em zidovudina (AZT) por ET AAS

The aim of this work was to compare the performances of the L'vov and integrated platforms in order to overcome the interferences found on lead determination in zidovudine by ET AAS. Pyrolysis and atomization temperatures found with integrated platform were 700 and 1400°C, respectively. The characteristic masses were 12.7 ± 1.2 pg with integrated platform and 11.1 ± 1.3 pg with grooved platform. The ratio between the slopes of zidovudine and aqueous curves shows a decrease in the interferences when the L'vov platform is used (bAZT/b aq = 0.97 ± 0.10) and the detection limit found was 0.03 µg.g-1. That ratio was 0.85 ± 0.07 with the integrated platform.

Influência da matéria orgânica na adsorção do fungicida triadimenol pelo solo

The adsorption of triadimenol (1-(4-chlorophenoxy)-3,3-dimethyl-1-(1H-1,2,4-triazol-1-yl)butan-2-ol) on soil samples with varying contents of organic matter was studied. The adsorption was described by means of the Freundlich's isoterm. An increase in the capacity of adsorption was observed as the content of organic carbon in the matrix increased. That effect was observed when removing the organic matter from the soil, when adding a urban waste compost to the soil sample as well as to the soil sample without organic matter, and also after leaving proportions of urban waste compost incubated in these matrices for a period of 120 days. The results show that the adsorption of the triadimenol in the soil is dependent of its content of organic carbon.

Influência de alguns parâmetros experimentais nos resultados de análises calorimétricas diferenciais - DSC

A series of experiments were performed in order to demonstrate to undergraduate students or users of the differential scanning calorimetry (DSC), that several factors can influence the qualitative and quantitative aspects of DSC results. Saccharin, an artificial sweetner, was used as a probe and its thermal behavior is also discussed on the basis of thermogravimetric (TG) and DSC curves.

Influência da mineralogia dos sedimentos das bacias hidrográficas dos rios Mogi-Guaçu e Pardo na composição química das águas de abastecimento público

This work studied bottom sediment from catchment area of 13 stations of water treatment of Mogi-Guaçu and Pardo river basins, through identification of mineralogical matrix and its correlation with potential bioavailable metal concentrations. The main clay minerals present were kaolinite and illite. The values of iron and manganese grades were derived from reddish-purple soil, which is rich of such elements. They had higher values on areas with weak vegetation cover compared with other areas linked with more vegetation density. Higher values of calcium at Campestrinho station (IG 69) were associated to occurrence by weathering of calcium feldspars markedly present on regional porphiritic acid rocks. The concentrations of phosphorous are characteristically high on areas near urbanized regions.

Influência da calcinação sobre a remoção de ferro da caulinita e ilita e seus efeitos sobre a acidez

Samples of natural clay composed by kaolinite, illite, goethite and quartz, were calcinated and submitted to lixiviation with citrate and chloridric acid in order to remove iron. Investigation due to extraction consequences was carried cut by analyzing its acid properties using ammonia gas as probe in infrared spectrophotometry analysis. The sample that were treated with citrate followed by acid lixiviation yield materials twice more acid than samples treated with acid only.

Influência do material do destilador na composição química das aguardentes de cana: parte II

The quantitative chemical analysis of the Brazilian sugar cane spirit distilled from glass column packaged with copper, stainless steel, aluminum sponge, or porcelain balls is described. The main chemical compounds determined by gas chromatography coupled with flame ionization (FID) and flame photometric (FPD) detectors and liquid chromatography coupled with diode array detector are aldehydes, ketones, carboxylic acids, alcohols, esters and dimethylsulfite (DMS). The spirits produced either in columns filled with copper or aluminum pot still exhibits the lowest DMS contents but the higher sulfate and methanol contents, whereas spirits produced in stainless steel or porcelain showed higher DMS concentration and lower teors of sulfate ion and methanol. These observations are coherent with DMS oxidation to sulfate, with methanol as by product, in the presence of either copper or aluminum.